SLI/CF heating problem?

im considering getting SLI/CF instead of a single powerful card for my new PC. i've done my research and i m worrying about cooling problems, there will be only 2 PCI slots between my PCI-E slots which means there will be only 1 PCI slot worth of space between the two cards, will it decrease cooling performance by a lot?
Also, do Nvidia have better SLI driver than AMD CF ones so they have better performance?

It depends on the PC case you have, the cooling setup of your case, the card models (coolers), ...

Game support for SLI and Crossfire is about equal, SLI a bit better perhaps.
But take care, many montherboards support Crossfire but do not support SLI (the board needs a certificate to have SLI support). That means - SLI boards cost a bit more.

And also there is the need for a stronger PSU than with a single card.

SLI/Crossfire pros:
- up to 80-90 % increase in performance in many games (compared to a single card like the ones used in CF/SLI)
- more performance for the same price in most cases (2 150$ cards outperform a single 300$ card)

cons:
- higher power draw (2 150$ cards usually consume more power than a single 300$ card)
- louder (more graphic cards to produce sounds)
- higher temperatures (in most cases there is not enough space/air between the cards)
- need for a stronger PSU (more money spent on the PSU)
- low performance increase in some cases (not all games support multi-gpu setups)
- sometimes you have to wait for new drivers to have SLI or CF support for new games
- There might bee other problems

Consider this:
If you want 2 250$ cards and a PSU for that setup, you need a PSU, lets say, for 150$. That is 650$ total.
If you go with a single card, you can buy a single card for 550$ and a PSU for 100$.
That single card may be stronger than these 2 cards in a multi-gpu setup and you end up with a quieter PC that consumes less power.

1. When two cards are placed right next to one another, it is more difficult for each card to intake cool air inside the case so theoretically temperatures will be higher than if it was just a single card configuration. Try and get a card that is able to exhaust the warm air externally as this will help decrease temps.

2. It's hard to say which video card drivers are better, it's usually a matter of opinion and it changes very often.

Since most of the members already gave good advice I just want to add that you should consider your ambient temp as well, even if you have a good cooling setup, if your case won't be able to suck in cool air then your temperatures won't drop. I crossfired two sapphire ref. 6870's before switching to a single gtx 560 ti, I was using a cooler master 690 2 advanced case w/ additional cm fans with an ambient temp of 25c and my cards still reach 80+ c and it was hot all over my case because its tight inside so there isn't enough space for the air to move around, so the size of your case is an important factor as well. If you are serious in getting CF/SLI and worried about the temps your best bet is to use a cutom water cooling setup. Simply put if you don't have a large case, good cooling setup and cool ambient temperature then you should consider just getting a single powerful card.